Initial commit: Custom Start Page application with authentication and DynamoDB storage

internal/auth/user_service.go

@@ -0,0 +1,100 @@
+package auth
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"time"
+
+	"github.com/google/uuid"
+	"golang.org/x/oauth2"
+
+	"custom-start-page/internal/models"
+	"custom-start-page/internal/storage"
+)
+
+// GoogleUserInfo represents the user info returned by Google
+type GoogleUserInfo struct {
+	ID            string `json:"id"`
+	Email         string `json:"email"`
+	VerifiedEmail bool   `json:"verified_email"`
+	Name          string `json:"name"`
+	Picture       string `json:"picture"`
+}
+
+// UserService handles user creation and retrieval
+type UserService struct {
+	userRepo *storage.UserRepository
+}
+
+// NewUserService creates a new user service
+func NewUserService(userRepo *storage.UserRepository) *UserService {
+	return &UserService{
+		userRepo: userRepo,
+	}
+}
+
+// GetOrCreateUserFromGoogle fetches user info from Google and creates or retrieves the user
+func (s *UserService) GetOrCreateUserFromGoogle(ctx context.Context, token *oauth2.Token, oauthConfig *oauth2.Config) (*models.User, error) {
+	// Fetch user info from Google
+	userInfo, err := s.fetchGoogleUserInfo(ctx, token, oauthConfig)
+	if err != nil {
+		return nil, fmt.Errorf("failed to fetch Google user info: %w", err)
+	}
+
+	// Check if user already exists
+	user, err := s.userRepo.GetByOAuthID(ctx, "google", userInfo.ID)
+	if err == nil {
+		// User exists, update last login time
+		user.UpdatedAt = time.Now()
+		if err := s.userRepo.Update(ctx, user); err != nil {
+			return nil, fmt.Errorf("failed to update user: %w", err)
+		}
+		return user, nil
+	}
+
+	// User doesn't exist, create new user
+	user = &models.User{
+		ID:            uuid.New().String(),
+		Email:         userInfo.Email,
+		OAuthProvider: "google",
+		OAuthID:       userInfo.ID,
+		CreatedAt:     time.Now(),
+		UpdatedAt:     time.Now(),
+	}
+
+	if err := s.userRepo.Create(ctx, user); err != nil {
+		return nil, fmt.Errorf("failed to create user: %w", err)
+	}
+
+	return user, nil
+}
+
+// fetchGoogleUserInfo fetches user information from Google's userinfo endpoint
+func (s *UserService) fetchGoogleUserInfo(ctx context.Context, token *oauth2.Token, oauthConfig *oauth2.Config) (*GoogleUserInfo, error) {
+	client := oauthConfig.Client(ctx, token)
+	
+	resp, err := client.Get("https://www.googleapis.com/oauth2/v2/userinfo")
+	if err != nil {
+		return nil, fmt.Errorf("failed to get user info: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		body, _ := io.ReadAll(resp.Body)
+		return nil, fmt.Errorf("failed to get user info: status %d, body: %s", resp.StatusCode, string(body))
+	}
+
+	var userInfo GoogleUserInfo
+	if err := json.NewDecoder(resp.Body).Decode(&userInfo); err != nil {
+		return nil, fmt.Errorf("failed to decode user info: %w", err)
+	}
+
+	if !userInfo.VerifiedEmail {
+		return nil, fmt.Errorf("email not verified")
+	}
+
+	return &userInfo, nil
+}